Former Playboy model Anna Nicole Smith was killed by a lethal combination of an accidental overdose of sleeping medication together with other prescription drugs, authorities in the US have announced.

Foul play had been ruled out and the case was effectively now closed, police said, ending weeks of speculation over her sudden death.

But the medical examiner said she might still be alive had she not refused to go to hospital when she was suffering from a raging fever three days earlier.

The sleeping medication chloral hydrate was ruled to be the main factor but it combined with several other drugs, including anti-depressants, to cause the 39-year-old’s death in a Florida hotel room in February.

In total, around nine prescription drugs were found in her blood though not all contributed to her death, the autopsy ruled.

An infection in her left buttock stemming from a previous injection of drugs, together with a case of flu, also contributed.

Addictive drugs such as opiates and cocaine were not found in the tragic starlet’s system, and there was no evidence of illegal drugs in the room where she was found unconscious, nor of disease.